From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v1 4/6] x86/hvm: Add SMAP support to HVM guest Date: Tue, 15 Apr 2014 11:36:51 +0100 Message-ID: <534D0BC3.5000407@citrix.com> References: <1397566922-19749-1-git-send-email-feng.wu@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1397566922-19749-1-git-send-email-feng.wu@intel.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Feng Wu Cc: jun.nakajima@intel.com, eddie.dong@intel.com, Ian.Campbell@citrix.com, JBeulich@suse.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 15/04/14 14:02, Feng Wu wrote: > Intel new CPU supports SMAP (Supervisor Mode Access Prevention). > SMAP prevents supervisor-mode accesses to any linear address with > a valid translation for which the U/S flag (bit 2) is 1 in every > paging-structure entry controlling the translation for the linear > address. > > This patch enable SMAP for HVM geust. > > Signed-off-by: Feng Wu > --- > xen/arch/x86/hvm/hvm.c | 3 +++ > xen/arch/x86/mm/guest_walk.c | 27 +++++++++++++++++++++++---- > xen/include/asm-x86/hvm/hvm.h | 13 +++++++++++++ > 3 files changed, 39 insertions(+), 4 deletions(-) > > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c > index b0da8e7..b52476d 100644 > --- a/xen/arch/x86/hvm/hvm.c > +++ b/xen/arch/x86/hvm/hvm.c > @@ -3036,6 +3036,9 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx, > if ( (count == 0) && !cpu_has_smep ) > *ebx &= ~cpufeat_mask(X86_FEATURE_SMEP); > > + if ( (count == 0) && !cpu_has_smap ) > + *ebx &= ~cpufeat_mask(X86_FEATURE_SMAP); > + > /* Don't expose MPX to hvm when VMX support is not available */ > if ( (count == 0) && > (!(vmx_vmexit_control & VM_EXIT_CLEAR_BNDCFGS) || > diff --git a/xen/arch/x86/mm/guest_walk.c b/xen/arch/x86/mm/guest_walk.c > index 70460b6..1d5f1fc 100644 > --- a/xen/arch/x86/mm/guest_walk.c > +++ b/xen/arch/x86/mm/guest_walk.c > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > > > /* Flags that are needed in a pagetable entry, with the sense of NX inverted */ > @@ -144,14 +145,18 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, > guest_l4e_t *l4p; > #endif > uint32_t gflags, mflags, iflags, rc = 0; > - int smep; > + int smep, smap; > bool_t pse1G = 0, pse2M = 0; > + unsigned long sel = 0; > + uint64_t eflags = guest_cpu_user_regs()->eflags; > p2m_query_t qt = P2M_ALLOC | P2M_UNSHARE; > > perfc_incr(guest_walk); > memset(gw, 0, sizeof(*gw)); > gw->va = va; > > + __vmread(GUEST_CS_SELECTOR, &sel); > + > /* Mandatory bits that must be set in every entry. We invert NX and > * the invalid bits, to calculate as if there were an "X" bit that > * allowed access. We will accumulate, in rc, the set of flags that > @@ -165,7 +170,21 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, > * whole walk as if it were a user-mode one and then invert the answer. */ > smep = (is_hvm_vcpu(v) && hvm_smep_enabled(v) > && (pfec & PFEC_insn_fetch) && !(pfec & PFEC_user_mode) ); > - if ( smep ) > + > + /* > + * SMAP: kernel-mode data accesses from user-mode mappings should fault > + * A fault is considered as a SMAP violation if the following > + * conditions come ture: > + * - X86_CR4_SMAP is set in CR4 > + * - An user page is accessed > + * - CPL = 3 or X86_EFLAGS_AC clear set) "X86_EFLAGS_AC clear set" ? What do you mean by this? ~Andrew > + * - Page fault in kernel mode > + */ > + smap = ( is_hvm_vcpu(v) && hvm_smap_enabled(v) > + && !(!((sel & 3) == 3) && (eflags & X86_EFLAGS_AC)) > + && !(pfec & PFEC_user_mode) ); > + > + if ( smep || smap ) > mflags |= _PAGE_USER; > > #if GUEST_PAGING_LEVELS >= 3 /* PAE or 64... */ > @@ -338,8 +357,8 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, > #if GUEST_PAGING_LEVELS >= 4 /* 64-bit only... */ > set_ad: > #endif > - /* Now re-invert the user-mode requirement for SMEP. */ > - if ( smep ) > + /* Now re-invert the user-mode requirement for SMEP and SMAP */ > + if ( smep || smap ) > rc ^= _PAGE_USER; > > /* Go back and set accessed and dirty bits only if the walk was a > diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h > index dcc3483..b703b93 100644 > --- a/xen/include/asm-x86/hvm/hvm.h > +++ b/xen/include/asm-x86/hvm/hvm.h > @@ -257,6 +257,8 @@ int hvm_girq_dest_2_vcpu_id(struct domain *d, uint8_t dest, uint8_t dest_mode); > (hvm_paging_enabled(v) && ((v)->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PAE)) > #define hvm_smep_enabled(v) \ > (hvm_paging_enabled(v) && ((v)->arch.hvm_vcpu.guest_cr[4] & X86_CR4_SMEP)) > +#define hvm_smap_enabled(v) \ > + (hvm_paging_enabled(v) && ((v)->arch.hvm_vcpu.guest_cr[4] & X86_CR4_SMAP)) > #define hvm_nx_enabled(v) \ > (!!((v)->arch.hvm_vcpu.guest_efer & EFER_NX)) > > @@ -363,6 +365,16 @@ static inline int hvm_event_pending(struct vcpu *v) > #define HVM_CR4_HOST_MASK (mmu_cr4_features & \ > (X86_CR4_VMXE | X86_CR4_PAE | X86_CR4_MCE)) > > +static inline bool_t hvm_cpuid_has_smap(void) > +{ > + unsigned int eax = 0, ebx = 0, ecx = 0, edx = 0; > + unsigned int leaf = 0x7; > + > + hvm_cpuid(leaf, &eax, &ebx, &ecx, &edx); > + > + return !!(ebx & cpufeat_mask(X86_FEATURE_SMAP)); > +} > + > /* These bits in CR4 cannot be set by the guest. */ > #define HVM_CR4_GUEST_RESERVED_BITS(_v) \ > (~((unsigned long) \ > @@ -371,6 +383,7 @@ static inline int hvm_event_pending(struct vcpu *v) > X86_CR4_MCE | X86_CR4_PGE | X86_CR4_PCE | \ > X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT | \ > (cpu_has_smep ? X86_CR4_SMEP : 0) | \ > + (hvm_cpuid_has_smap() ? X86_CR4_SMAP : 0) | \ > (cpu_has_fsgsbase ? X86_CR4_FSGSBASE : 0) | \ > ((nestedhvm_enabled((_v)->domain) && cpu_has_vmx)\ > ? X86_CR4_VMXE : 0) | \